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<head>
    <meta charset="UTF-8">
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    <title>11-翻转数组</title>
</head>
<body>
    <script>
             // 将数组 ['关羽', '张飞', '程咬金', '吕布']; 的内容反过来存放
             // ['吕布', '程咬金', '张飞', '关羽']
        let arr = ['关羽', '张飞', '程咬金', '吕布'];
        let arr1 = [];
        let arr2 = [];
        /* 
            index0   index1
                0       3
                1       2
                2       1
                3       0
            index0 + index1 = 3或者(arr.length -1)
            index1 = arr.length -1 - index0
        */
       for (let index in arr){
        //    console.log(index,arr[index]);
           arr1[arr.length - 1 -index] = arr[index];
       }
       console.log(arr1);

       
       console.log('--------方案2----------');
    //  倒叙遍历数组，再将元素放入新数组。
    for (let i = arr.length -1; i >=0; i--){
        // 倒叙遍历
        // console.log(i,arr[i]);
        arr2[arr2.length] = arr[i];
    }
    console.log(arr2);
    </script>
</body>
</html>